1. Field of the Invention
The present invention relates to a chuck which holds an object such as an electric component and also to an electric-component mounting system which mounts an electric component on a circuit substrate such as a printed wiring board.
2. Discussion of Related Art
There is known an electric-component (EC) mounting system which includes a chuck for holding an electric component (EC) and moves the chuck holding the EC to a circuit substrate to mount the EC on the substrate and thereby produce an electric circuit. The conventional chuck includes a pair of holding jaws, and an opening and closing device for mechanically opening and closing the jaws by moving the jaws symmetrically with respect to the center of the chuck. Thus, the chuck can hold the EC such that the center of the EC is aligned with that of the chuck.
However, the conventional chuck including the mechanical opening and closing device cannot largely change the respective positions of the holding jaws because of the mechanical structure of the opening and closing device. Therefore, the conventional chuck cannot hold different sorts of ECs having largely different sizes. In addition, the chuck cannot hold an EC having an asymmetric shape such that a desired portion of the EC is aligned with the centerline of the chuck.
While the above discussion relates to the chuck for holding the EC, the same problems as indicated above occur to other sorts of chucks for holding other sorts of objects.
The present invention provides a linear-motor-driven chuck and an electric-component mounting system which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (13). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided a chuck for holding an object, comprising at least one linear motor which includes at least one linear stator, two moving members which are movable along the linear stator, independent of each other, and at least one guide member which guides each of the two moving members along the linear stator; and two holding members which are supported by the two moving members, respectively, and which cooperate with each other to hold the object.
The linear motor may include a single linear stator common to the two moving members, or two linear stators for the two moving members, respectively. In the former case, each one of the two moving members may be moved over the middle or center of the single linear stator, toward the other moving member. In the latter case, the linear motor can be said as two linear motors each of which includes a corresponding one of the two linear stators and a corresponding one of the two moving members.
In the present chuck, the two holding members are supported by the two moving members of the linear motor that are movable independent of each other. Therefore, the distance between the two holding members can be largely changed more easily than the conventional chuck including the mechanical opening and closing device. Thus, the present chuck can hold various sorts of objects in a wider range. The two holding members may be two external holding members which externally engage an outer surface or surfaces of an object and thereby hold it, or two internal holding members which engage an inner surface or surfaces of an object having an inner space and thereby hold it.
(2) According to a second feature of the present invention that includes the first feature (1), the chuck further comprises a rotating device which rotates the linear motor about an axis line perpendicular to a lengthwise direction of the linear stator.
Since the present chuck includes the chuck rotating device which rotates the linear motor, the chuck can change the current angular phase of the object (e.g., electric component, EC) held by the two holding members, to any desirable angular phase. For example, the chuck can change the current angular phase of an EC to a prescribed angular phase thereof relative to a circuit board, before the EC is mounted on the board.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), each of the two moving members comprises an attaching member to which a corresponding one of the two holding members is detachably attached.
Since the two holding members are detachably attached to the respective attaching members of the two moving members, the current sort of holding members may be replaced with a new sort of holding members, depending upon the sort of new objects to be held next by the chuck. Thus, the present chuck can hold various sorts of objects in a wider range.
(4) According to a third feature of the present invention that includes any one of the first to third features (1) to (3), the chuck further comprises two position sensors each of which detects a current position of a corresponding one of the two moving members and produces a detection signal indicating the detected current position of the one moving member.
Since the two position sensors detect the respective current positions of the two moving members, a control device, for example, which may be employed and connected to the linear motor can more accurately control, based on the detected current positions, the respective current positions of the two moving members of the linear motor. This contributes to improving a positioning accuracy with which the chuck holds the object.
(5) According to a fifth feature of the present invention that includes any one of the first to fourth features (1) to (4), the chuck further comprises two origin sensors each of which detects a corresponding one of the two moving members which is currently positioned at an origin position thereof.
Since the two origin sensors detect the two moving members being currently positioned at their origin positions, the above control device can control, based on the detected origin positions, the respective movements of the two moving members of the linear motor. This contributes to facilitating the control to open and close the chuck.
(6) According to a sixth feature of the present invention that includes the fourth or fifth feature (4) or (5), the chuck further comprises a control device including a symmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members symmetrically with respect to a centerline of the chuck.
The present chuck can hold an object symmetric with respect to a plane, in a state in which the plane contains a centerline of the chuck.
(7) According to a seventh feature of the present invention that includes any one of the fourth to sixth features (4) to (6), the chuck further comprises a control device including an asymmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members asymmetrically with respect to a centerline of the chuck.
The present chuck is suitable for holding an asymmetric object.
(8) According to an eighth feature of the present invention that includes any one of the fourth to seventh features (4) to (7), the chuck further comprises a control device including an object-dependent control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members to respective opened positions where the two holding members supported by the two moving members are distant from each other by a distance greater than a prescribed dimension of the object by a predetermined distance and then move the two moving members toward each other at respective speeds equal to each other.
The present chuck can hold, or release, the object in a short time, and can position, and hold, the object at a desired position.
(9) According to a ninth feature of the present invention that includes any one of the first to eighth features (1) to (8), the chuck further comprises a control device including a holding-force control portion which controls a holding force with which the two holding members hold the object.
The present chuck can hold, with an appropriate holding force, an object which is easily deformable or highly fragile.
(10) According to a tenth feature of the present invention that includes any one of the first to ninth features (1) to (9), the chuck comprising two linear motors one of which includes two first moving members that are movable toward, and away from, each other in a first direction and the other of which includes two second moving members that are movable toward, and away from, each other in a second direction perpendicular to the first direction, and the first and second moving members cooperate with each other to hold the object in the first and second directions.
The present chuck can more reliably hold the object and, in particular, it is advantageous for holding an object having a shape asymmetric with respect to both of two planes which are respectively perpendicular to the first and second directions.
(11) According to an eleventh feature of the present invention, there is provided a system for mounting at least one electric component on a circuit substrate, comprising a chuck according to any one of the first to tenth features (1) to (10); a chuck moving device which moves the chuck to an arbitrary position in a movement area parallel to a substantially horizontal plane; a supplying device which is provided in the movement area and which supplies the electric component to the chuck; and a supporting device which is provided in the movement area and which supports the circuit substrate on which the electric component is to be mounted by the chuck.
Since the present EC mounting system employs the chuck which can hold various sorts of objects in a wide rage as described above, the mounting system enjoys a high degree of freedom in the meaning that it can mount various sorts of ECs on a circuit substrate.
(12) According to a twelfth feature of the present invention that includes the eleventh feature (11), the mounting system further comprises a chuck elevating and lowering device which elevates and lowers the chuck in respective directions perpendicular to the substantially horizontal plane.
Since the present EC mounting system includes the chuck elevating and lowering device which elevates and lowers the chuck, the mounting system can lower and elevate the chuck to take an EC from the EC supplying device and/or mount the EC on the circuit substrate. Therefore, the present mounting system need not lower or elevate the EC supplying device or the substrate supporting device to take out the EC from the supplying device or mount the EC on the circuit substrate supported by the supporting device. Thus, the overall construction of the EC mounting system can be simplified.
(13) According to a thirteenth feature of the present invention that includes the eleventh or twelfth feature (11) or (12), the mounting system further comprises an image taking device which takes an image of the electric component held by the chuck; and a modifying device which determines, based on image data representing the image taken by the image taking device, at least one positional error of the electric component held by the chuck and modifies, based on the determined positional error, at least one movement amount of the chuck moving device so as to move the chuck to a position where the positional error of the electric component is zero relative to the circuit substrate supported by the supporting device.
In the case where the EC held by the chuck has at least one positional error (e.g., a horizontal-position error in an X-axis direction or a Y-axis directioin, and/or an angular-phase error about a Z axis perpendicular to the X and Y axes), the present EC mounting system can mount the EC on the circuit substrate after correcting the positional error or errors. Thus, the present mounting system enjoys a high accuracy with respect to the position or positions at which the system mounts the EC on the circuit substrate. However, as described above, the chuck can enjoy a high accuracy with respect to the position or positions at which the chuck holds the EC. In the latter case, the image taking device and the modifying device may be omitted, and the chuck according to the tenth feature (10) is particularly advantageous. According to the combination of the thirteenth and tenth features (13) and (10), the EC mounting system may employ, in place of the modifying device, a correcting device which determines, based on the image data representing the image taken by the image taking device, one or more positional errors of the EC held by the two pairs of moving members and corrects, based on the determined positional error or errors, the erroneous position or positions of the EC, by correcting the respective current positions of the two pairs of moving members. In the last case, it is preferred that each pair of moving members which are moved toward, and away from, each other in first directions be moved by a small distance in each of second directions perpendicular to the first directions, and be biased toward respective neutral positions thereof by respective biasing members such as elastic members. In this case, when the respective current positions of the one or first pair of moving members are corrected by moving those members, the other or second pair of moving members follow the movement of the first pair of moving members.